A growing sex abuse scandal is rocking the world's largest national congregation of Catholics. This week a Brazilian priest was given a lengthy jail sentence after a court heard extracts from a diary that read like a paedophile priest's how-to manual. A magazine earlier published evidence that, according to estimates by Vatican investigators, one in 10 of Brazil's priests was involved in some form of sexual misdemeanour.

The signs of abuse in a country that is home to about 125 million Catholics will be of particular concern to the church hierarchy. Until now Catholic leaders have comforted themselves with the belief that, no matter how battered its reputation in rich nations such as the United States, the church continued to be held in high esteem in the developing world.

Next week the Vatican is expected to publish formally details of a clampdown on the recruitment of gay priests aimed at quelling concerns that the church has become a refuge for paedophiles. However, in Brazil many of the claims relate to heterosexual abuse.

Regina Soares Jurkwicz, author of Unveiling the Politics of Silence: Sexual Abuse of Women by Priests in Brazil, said the South American country could now be facing a problem of even greater dimensions than that uncovered in the US in 2002.

"The Catholic church doesn't know what to do," she said. "In Brazil the [typical] reaction of the Catholic hierarchy is first to try to cover up the problem or discredit the witness.

"Then, it is to transfer the priest to another community, which is not told why he was transferred there."

Ms Jurkwicz said the problem had been exacerbated by the vast social divide between Brazil's haves and have-nots. "The victims are almost always poor, vulnerable people," she said, arguing that Brazil's wealth gap made it easier for priests to exploit youngsters with impunity.

Media reports in both Brazil and Italy have indicated that a special Vatican commission visited the country in September to investigate reports of a 70% leap in the number of priests involved in cases of sexual misbehaviour.

The Vatican's inquiry - carried out by the Congregation for the Doctrine of Faith, the "ministry" that inherited the responsibilities of the Inquisition - appears to have confirmed its worst fears. According to extracts from its report, carried in Brazil's IstoE magazine, 10% of Brazil's priests - some 1,700 clerics - were involved in cases of sexual misconduct, including the physical abuse of children and women.

The study was also said to have found that in the last three years at least 200 Brazilian priests had been referred to church psychological institutions following cases involving paedophilia. Ten clerics were in jail and a further 40 were on the run from the law.

On Thursday Father Tarcisio Tadeu Spricigo was jailed for 14 years and eight months for sexually abusing two boys, one of them a five-year-old. In his diary, obtained by police in Sao Paulo, the 48-year-old priest stressed the need "to have boys who can keep a secret and without sexual scruples".

He recommended: "Always present oneself as the dominator. Be caring and not hurried. Never ask questions, but have certainties. Get secure and needy boys, who don't have fathers and who are poor. Never get involved with rich kids."

Ms Jurkwicz said: "The number of cases seems to be rising ... [but] this is not a new problem. It has just been something that nobody dared talk about and, to a certain extent, that is still the way it is."

Spreading malaise

· In January 2002 Cardinal Bernard Law, the archbishop of Boston, set off the worst sex abuse crisis in the church's history when he admitted to having reassigned abusive priests to new parishes instead of reporting them to police.

· An unprecedented number of victims subsequently came forward, leading to court cases that have devastated the US church's finances. In 2003 the Boston archdiocese agreed to pay $85m to more than 500 victims.

· In April 2002 attention switched to Ireland when Brendan Comiskey, bishop of Ferns, resigned over his handling of allegations against two priests. Scandals later erupted in the Dublin archdiocese.

· Just weeks before his election Pope Benedict XVI shocked some Catholics, and delighted others, by referring to the "filth" in